Why hasn’t he completely removed his ex from his life?

So I was seeing this guy for nearly a year before finding out that he had a girlfriend (long term, lived with her, they were both on lease, was still sleeping with her, saying he loved her and going home to her every night etc) the whole time. I know I should have just ended it and told him never to contact me again, but I had fallen in love with him. I decided to message his girlfriend and advise her of what had been going on, giving her a choice in this situation. The day I sent that text, he left her and has been living with me ever since. For the first week he was a mess of a man, who cried for days and just became a shell of who i had fallen for. It has occurred to me that I was selfishly thinking of myself and not the gfs or his feelings when i sent that text. I had serious trust issues with him for the first couple of months to the point I was tracking his every movement on my phone.

While I have blocked his ex on socials, and he has removed her off snapchat - I am aware that he is still friends with her on fb, her ph number isn’t blocked and he is checking her fb stories every time she posts something. He has not communicated directly with her.

Should I be concerned that he has not completely removed his ex from his life? Or is he just trying not to cause anymore hurt by blocking etc? Does he look at the stories because he wants to know she is doing ok, or is he missing her and wants to know what she is doing but from a distance. He has been with me and living with me now for 7mths.

No judgement please, just wanted to know if anyone else has experienced this or a male can provide me with some insight?
Updates
1 y
I forgot to add, that round end of march he sent his ex this message:

I'm sorry
for everything. I want you
to know that I did 100% and whole heartedly love you and some part of me always will. I'll never forgive myself for what I did to you. You were a massive part of my life and I'll never forget about you or the 3 furballs. I do miss you an nala and I guess patch too. Thankyou for being you and a part of my life and I'm sorry for not being the man you deserve.

Why hasn’t he completely removed his ex from his life?
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